Wall mountable electric heater with slim form factor

ABSTRACT

A wall mountable electric heater comprises a core  20  arranged in a casing  2  with a convection space  50  defined between opposed surfaces  47, 27′  of the casing and the core, The opposed surfaces are provided with oppositely directed protrusions  26, 44  which are spaced apart in two dimensions and arranged in-between one another to form a serpentine flowpath. The protrusions  44  in the panel  4  of the casing define recesses  43  which extend inwardly towards the core, each recess having a base wall  46  in which a perforation  48  is formed between the first and second sides  40, 41  of the panel  4,  The air flowing upwardly through the convection space  50  generates a pressure differential across the first and second sides  40, 41  of the panel  4,  drawing air in through the perforations to increase the mass flow rate of the air in the convection space. The base wall  46  of each recess may be spaced apart from the opposed, outwardly facing side  23  of the core by a relatively small distance D 1,  increasing the velocity of the airflow and hence the pressure differential proximate the perforation  48.

This invention relates to wall mounted electric heaters of the typecomprising a thermal mass, for example, a block of soapstone, heated byan electric element.

The thermal mass absorbs heat from the electic element and emits theheat at a comfortable temperature by radiation and/or convection. Suchheaters may be arranged to store heat energy at night and then emit itduring the day, or with a smaller thermal mass to emit the stored heatover a much shorter cycle time so that the element is energisedintermittently while the heater is in use.

Typically the thermal mass is arranged as a core within an outer casingwhich is mounted on a wall of the room into which the heat is emitted.It is desirable for the whole assembly to be as slim as possible so asnot to obstruct the room; however, the casing must accommodate aconvector structure which generates enough airflow to transfer theconvective heat output into the room.

It is a general object of the present invention to provide an electricheater with an effective convector structure in a slim form factor.

According to the present invention there is provided a wall mountableelectric heater as defined in the claims.

The novel heater comprises a casing and a core arranged in the casing.The casing includes a panel with opposite, first and second sides. Thecore includes a first outward side, a thermal mass, and an electricelement arranged to heat the thermal mass. Respective surfaces of thesecond side of the panel and the first outward side of the core arespaced apart in opposed relation on opposite sides of a nominalconvection plane lying in a convection space between the panel and thecore.

The first outward side of the core has a plurality of first protrusionswhich are spaced apart in two dimensions to form a spaced array. Thepanel has a plurality of recesses which are spaced apart in twodimensions to form a spaced array on the first side of the panel, eachrecess extending along a recess axis towards the first outward side ofthe core to define a second protrusion on the second side of the panel.

Each recess has a recess sidewall and a recess base wall. The recesssidewall surrounds the recess axis and extends towards the first outwardside of the core and terminates at the recess base wall. The recess basewall is spaced apart from the first outward side of the core by aseparation distance D1.

When the first and second protrusions are projected onto the convectionplane, the first protrusions are arranged in-between the secondprotrusions in the convection plane so that the convection space definesa serpentine flowpath between respective adjacent ones of the first andsecond protrusions. A perforation is formed in each recess base wallbetween the first and second sides of the panel.

As air flows upwards through the convection space between the recessbase wall and the first outward side of the core, its velocity generatesa pressure differential across the first and second sides of the panelso that air is drawn in through the perforations, increasing the massflow rate of air within the convection space. The serpentine flowpathincreases heat transfer into the air flowing over the core. A relativelysmall separation distance D1 increases the differential velocity of theairflow so that more effective convective heat transfer is obtained in aslim form factor.

Further features and advantages will be appreciated from the followingillustrative embodiment of the invention which will now be described,purely by way of example and without limitation to the scope of theclaims, and with reference to the accompanying drawings, in which:

FIGS. 1, 2, 3 and 4 are respectively a front, side, back and top view ofa wall mountable electric heater in accordance with an embodiment of theinvention;

FIGS. 5 and 6 are respectively a back view and a front view of the corewith the front convector structure attached to it;

FIG. 7 is a rear view of the heater showing the core in its installedposition inside the casing;

FIG. 8 is a vertical section through the heater at VIII-VIII of FIGS. 7and 10;

FIG. 9 is another rear view of the heater and core showing how air isdrawn in through the perforations;

FIG. 10 is a horizontal section at X-X of FIG. 7;

FIG. 11 is an enlarged view of FIG. 8 showing how air is drawn inthrough the perforations;

FIG. 12 is an enlarged view of the central region of FIG. 10; and

FIG. 13 is another horizontal section through the central region of theheater taken just below the view of FIG. 12 at XIII-XIII of FIG. 7.

Reference numerals and characters appearing in more than one of thefigures indicate the same or corresponding features in each of them.

Referring to the figures, the heater or radiator 1 comprises a casing 2and a core 20 arranged inside the casing. The casing 2 may be made fromsheet metal, advantageously sheet aluminium, comprising a front panel 3which defines the front side of the heater, and a rear panel 4 whichdefines a rear surface of the casing. The front and rear panels may bejoined by internal sides 5 which are covered by end covers 6. A topcover 7 with air vents 8 is arranged over the top of the verticalpanels. The casing is provided with feet 9 which support the lower endof the casing above the level of the floor, the lower end defining anopening 10 through which air can flow into the casing at the base. Thecasing also has supports 11 which are used with suitable brackets orother wall fixings (not shown) as known in the art to support the heateron a wall 12 with the rear surface in spaced parallel relation to thewall as shown in FIG. 11.

As best seen in FIGS. 12 and 13, the core 20 may comprise a casing 21,which may be made for example from aluminium or other sheet metal,having a rear part 22 which defines a first, rearwardly facing outwardside 23 of the core, and a front part 24 which defines a second,frontwardly facing outward side 25 opposite the first outward side. Thefirst and second parts may be formed as two shallow trays with fittogether with their sidewalls in overlapping relation to form a shellwhich encloses the thermal mass 30 between the front and rear sides 25,23.

The thermal mass 30 may comprise any suitable material that can storeheat and release it at a comfortable temperature, for example, acompressed block of mineral powder such as soapstone, An electricelement 31 is arranged to heat the thermal mass 30, conveniently byembedding the element inside the block. A power conductor 32 is arrangedin communication with suitable thermostatic controls or othertemperature sensing and control means (not shown) as known in the artfor sensing the temperature of the core and/or the temperature of theair in the room to energise the element and control the temperature ofthe core so as to emit heat at a comfortable temperature by radiationand convection through the casing.

The rearwardly facing outward side 23 of the core defines a plurality offirst protrusions 26 which are spaced apart in two (respectively,vertical and horizontal) dimensions to form a spaced array as shown inFIG. 5. The first protrusions may be formed as locally indented regionsof a generally flat sheet metal panel 27 forming the major surface ofthe rear part 22 of the casing. Each first protrusion may extendoutwardly from the flat surface 27′ of the panel 27 as shown along anaxis X2 to define a frustoconical sidewall 28 defining a surface ofrevolution about the axis X2 with a flat top surface 29 normal to theaxis X2 and so parallel with the convection plane P1 and the flatsurface 27′ of the panel 27. The two dimensions defining the spacedarray extend in the major flat surface plane 27′ of the panel 27parallel with the convection plane P1, hence in the plane of the drawingas shown in FIG. 5.

The thermal mass 30 may be arranged as shown in the sheet metal casing21 in contact with regions of the sheet metal panel 27 defining on itsoutward side 23 its flat surface 27′ proximate the first protrusions 26,a void 33 being formed between the thermal mass 30 and each of the firstprotrusions 26 as shown. Despite the presence of the void 33, theintimate contact between the flat portion of the panel 27 and thethermal mass 30 is found to effectively transfer heat to the firstprotrusions 26 and hence to the air which impinges on the firstprotrusions as it flows through the convection space 50. The heattransfer from the core to the first protrusions is particularlyeffective when the panel 27 is made from aluminium, providing aneffective but economical construction which makes it possible to formthe thermal mass 30 by pressing as a simple, rectilinear block.

The rear panel 4 may be formed from sheet metal, e.g. sheet aluminium,and is locally indented to define a plurality of recesses 43 which arespaced apart in two (respectively, vertical and horizontal) dimensionsto form a spaced array on the first side 40 of the panel. The opposite,first and second sides 40, 41 of the rear panel 4 may be generally flatin the regions between the recesses 43 to extend in parallel with theconvection plane P1, hence defining a flat surface 47 on its second side41 in-between the second protrusions 44. The two dimensions defining thespaced array extend in the major plane of the panel 4 and parallel withthe convection plane P1, hence in the plane of the drawing as shown inFIG. 3.

Each recess 43 extends along a recess axis X1 towards the first outwardside 23 of the core to define a second protrusion 44 on the second side41 of the panel. Each recess has a recess sidewall 45 and a recess basewall 46, the recess sidewall 45 surrounding the recess axis X1 andextending towards the first outward side 23 of the core and terminatingat the recess base wall 46 as best seen in FIGS. 11, 12 and 13. Eachrecess sidewall 45 may define a frustoconical surface of revolutionabout the respective recess axis X1 as shown. A perforation 48 isformed, conveniently as a circular hole as shown, in each recess basewall 46 so that it extends along the recess axis X1 between the firstand second sides 40, 41 of the panel 4.

The core 20 is arranged in the casing 2 as shown so that each recessbase wall 46 is spaced apart from the first outward side 23 of the coreby a separation distance D1 (FIG. 12).

The flat surfaces 47 and 27′ (being respectively the flat surface 47 ofthe second side 41 of the rear panel 4 in-between the second protrusions44, and the flat surface 27′ of the outward side 23 of the rear panel 27in-between the first protrusions 26) are spaced apart in opposedrelation on opposite sides of a nominal convection plane P1 (FIG. 12)lying in a convection space 50 between the rear panel 4 and the core 20.In the installed position of the heater the convection plane P1 isvertical and parallel with the wall 12 (FIG. 11).

When the first and second protrusions 26, 44 are projected onto theconvection plane P1, the first protrusions 26 are arranged in-betweenthe second protrusions 44 in the convection plane P1 so that theconvection space 50 defines a serpentine flowpath between respectiveadjacent ones of the first and second protrusions 26, 44.

Advantageously as shown, the first and second protrusions 26, 44 mayintersect the convection plane. This improves the effectiveness of theserpentine flowpath so that air cannot flow in a straight line in theconvection plane P1 between the first and second protrusions, but ratheris diverted around each protrusion.

The projected positions of the first and second protrusions can be seenin FIG. 12 which shows how both sets of protrusions intersect theconvection plane P1; if in alternative embodiments the protrusions 26,44 are arranged entirely on opposite sides of the nominal convectionplane P1 they can nevertheless be projected onto the convection planeplane in a direction normal to the convection plane, so that when viewedin the convection plane the two sets of first and second projections 26,44 can be seen to be arranged in-between one another as shown in FIG. 7.

It can be seen that the respective surfaces 47, 27′ of the second side41 of the panel and the outward side 23 of the core are spaced apart bya distance D2 in opposed relation on opposite sides of the convectionplane P1.

In use, air is drawn into the convection space 50 via the opening 10 atthe base of the casing 2, travelling up through the convection space toexit via the air vents 8 in the top cover 7, as shown in FIGS. 9 and 11.The differential velocity of the upwardly flowing air relative to thestill air in the region between the rear panel 4 and the wall 12 createsa pressure differential, the restricted region of the convection spaceadjacent each perforation functioning in the manner of a Venturi oreductor to draw air in through the perforations 48 to increase the massflow rate of the air inside the convection space 50.

Although the invention is not bound by theory, it is believed that theserpentine flowpath may increase thermal transfer by causing the air toimpinge on the first protrusions 26 and by increasing the length of theflowpath and hence the residence time of the air within the convectionspace 50. Moreover, as air is drawn in through the perforations into theconvection space 50 as shown in FIGS. 9 and 11, the mass flow rate mayincrease progressively towards the top of the convection space 50 and sovelocity may also increase, which in turn accentuates the pressuredifferential driving more air into the convection space towards theupper end of the structure. The novel structure thus generates asurprisingly effective convective airflow in a very slim space with amaximum thickness dimension D2.

A relatively small separation distance D1 increases the differentialvelocity of the airflow so that more effective convective heat transferis obtained in a slim form factor. Advantageously therefore, and asshown, D1 may be less than D2. Optionally, also as shown, D1 may be lessthan 0.5·D2. For example, D1 may be about 0.4·D2 as shown, or about0.3·D2, or even less. By way of example, in some embodiments thedistance D1 may be in the range from about 5 mm to about 15 mm, forexample, about 1 cm.

In the illustrated embodiment, the front panel 3 of the casing 2 isspaced apart from the core 20 to define a front convector space 60between the front panel 3 and the core 20. A convector structure isarranged in the front convector space 60, the convector structurecomprising a plurality of walls 61 extending between the second,frontwardiy facing outward side 25 of the core and the front panel 3 ofthe casing, the walls 61 being spaced apart to divide the frontconvector space into a plurality of channels 62. Although in theillustrated embodiment the walls 61 are separate from the front panel 3,they could be incorporated into the front panel 3 so that the frontpanel 3 has a visible structure of vertical joints. Of course, otherconstructions are possible.

As best seen in FIG. 11, the convection space 50 may include a lowerregion 51 and an upper region 52, wherein in use, air heated in thelower region 51 flows upwardly into the upper region 52, and wherein thefirst and second protrusions extend into the lower region 51 but not theupper region 52.

When the novel heater 1 is mounted on a wall 12 with its rear surface inspaced parallel relation to the wall as shown in FIG. 11, the air drawnthrough the perforations 48 into the convection space 50 causes coolerair to flow upwardly from floor level and inwardly into the spacebetween the rear surface of the heater and the wall. In tests it isfound that the maximum temperature of the wall surface behind the heater1 remains surprisingly low while the heater is in use, being onlyslightly higher than that measured at some horizontal distance from theheater 1. Thus, the novel heater loses very little heat to the wall.

Further advantageously, the strong convective airflow generated by thenovel heater is found to reduce the surface temperature of the casing 2to a surprisingly low temperature, so that the novel heater may besuitable for use where conventional heaters with higher surfacetemperatures would present a risk of injury to vulnerable users.

In tests, it is found that as little as 5% of the heat output of thenovel heater may be radiated from its rear face opposite the wall, with25% being radiated from its front face and the remaining 70% beingtransferred to the room by the convected air flowing from the airoutlets which open at the top of the heater 1 from the rear convectionspace 50 and front convector space 60.

As illustrated, the recess base wall 46 is defined by an inwardly facingsurface, which is to say, a surface facing towards the core 20, whichmay be formed (wholly or in part) by the thickness of the recesssidewall 45. The recess base wall 46 may also define a rearwardly facingsurface, i.e. a surface facing away from the core 20, as shown.

In a development (not shown), the perforations 48 may be made somewhatlarger than illustrated, for example, extending up to most or all of theradially inner dimension (or diameter) of the recess 43 at the recessbase wall 46, in which case the recess base wall 46 may not have arearwardly facing surface.

In a further development (not shown), the surface temperature of thefront face of the heater may be further reduced by increasing the numberof walls 61 to further subdivide the front convector space 60, thusstrengthening the convection in the channels 62.

In a further development, the vertical (height) dimension of the upperregion 52 may be somewhat greater than illustrated. For example, theupper region 52 may be about 150 mm in height. The vertically elongatedupper region 52 acts as a chimney which further strengthens theconvective airflow through the convection space 50. In sucharrangements, further perforations (not shown) may be provided in therear panel 4 opening into the upper region 52 of the convection space50. This further increases the airflow drawn into the convection space50 from the space between the heater 1 and the wall 12.

When these features are provided in combination it is found that themaximum wall surface temperature behind the heater 1 may be as little as0.5° C. higher than that measured at a horizontal distance of 1.5 m awayfrom the heater 1.

In summary, a wall mountable electric heater comprises a core 20arranged in a casing 2 with a convection space 50 defined betweenopposed surfaces 47, 27′ of the casing and the core. The opposedsurfaces are provided with oppositely directed protrusions 26, 44 whichare spaced apart in two dimensions and arranged in-between one anotherto form a serpentine flowpath. The protrusions 44 in the panel 4 of thecasing define recesses 43 which extend inwardly towards the core, eachrecess having a base wall 46 in which a perforation 48 is formed betweenthe first and second sides 40, 41 of the panel 4. The air flowingupwardly through the convection space 50 generates a pressuredifferential across the first and second sides 40, 41 of the panel 4,drawing air in through the perforations 48 to increase the mass flowrate of the air in the convection space. The base wall 46 of each recessmay be spaced apart from the opposed, outwardly facing side 23 of thecore by a relatively small distance D1, increasing the velocity of theairflow and hence the pressure differential proximate the perforation48.

In alternative embodiments, the panel defining the recesses may bearranged other than at the rear surface of the casing, Instead of aconventional front convector structure as shown, two panels definingrecesses and protrusions might be arranged, one in front and one behindthe core, with the frontwardly facing side of the core also defining anarray of protrusions similar to the first protrusions, to define twoparallel convection spaces, each having a slim thickness dimension D2 asdescribed above, to further reduce the overall thickness of the heater.The first protrusions and the recesses defining the second protrusionscould be formed by pressing, moulding or any other suitable process. Therecesses and first and second protrusions could be other thanfrustoconical. If desired, the thermal mass could be pressed, moulded,cut or otherwise formed to define the first protrusions. The surface ofthe thermal mass could be exposed at the convection space without theuse of a sheet metal casing, The thermal mass could be a solid or liquidmaterial. The overall form factor of the heater can be selected to suitthe intended use position, being relatively taller and narrower orshorter and wider than that illustrated.

Many further adaptations are possible within the scope of the claims.

In the claims, reference numerals and characters in parentheses areprovided purely for ease of reference and should not be construed aslimiting features.

1. A wall mountable electric heater (1) comprising a casing (2) and acore (20) arranged in the casing (2); the casing (2) including a panel(4), the panel (4) having opposite, first and second sides (40, 41); thecore (20) including a first outward side (23), a thermal mass (30), andan electric element (31) arranged to heat the thermal mass (30);respective surfaces (47, 27′) of the second side (41) of the panel (4)and the first outward side (23) of the core (20) being spaced apart inopposed relation on opposite sides of a nominal convection plane (P1)lying in a convection space (50) between the panel (4) and the core(20); the first outward side (23) of the core (20) having a plurality offirst protrusions (26), the first protrusions (26) being spaced apart intwo dimensions to form a spaced array; the panel (4) having a pluralityof recesses (43), the recesses (43) being spaced apart in two dimensionsto form a spaced array on the first side (40) of the panel (4); eachrecess (43) extending along a recess axis (X1) towards the first outwardside (23) of the core (20) to define a second protrusion (44) on thesecond side (41) of the panel (4); each recess (43) having a recesssidewall (45) and a recess base wall (46), the recess sidewall (45)surrounding the recess axis (X1) and extending towards the first outwardside (23) of the core (20) and terminating at the recess base wall (46),the recess base wall (46) being spaced apart from the first outward side(23) of the core (20) by a separation distance D1; wherein, when thefirst and second protrusions (26, 44) are projected onto the convectionplane (P1), the first protrusions (26) are arranged in-between thesecond protrusions (44) in the convection plane (P1) so that theconvection space (50) defines a serpentine flowpath between respectiveadjacent ones of the first and second protrusions (26, 44); and aperforation (48) is formed in each recess base wall (46) between thefirst and second sides (40, 41) of the panel (4).
 2. A wall mountableelectric heater (1) according to claim 1, wherein the first and secondprotrusions (26, 44) intersect the convection plane (P1).
 3. A wallmountable electric heater (1) according to claim 1, wherein saidrespective surfaces (47, 27′) of the second side (41) of the panel (4)and the first outward side (23) of the core (20) are spaced apart by adistance D2 in opposed relation on opposite sides of the convectionplane (P1); and D1<D2.
 4. A wall mountable electric heater (1) accordingto claim 3, wherein D1<0.5·D2.
 5. A wall mountable electric heater (1)according to claim 1, wherein each recess sidewall (45) defines afrustoconical surface of revolution about the respective recess axis(X1).
 6. A wall mountable electric heater (1) according to claim 1,wherein the panel (4) defines a rear surface of the casing (2), and theheater (1) comprises supports (11) for supporting the heater (1) on awall (12) with the rear surface in spaced parallel relation to the wall(12).
 7. A wall mountable electric heater (1) according to claim 6,wherein the core (20) has a second outward side (25) opposite the firstoutward side (23), and the casing (2) includes a front panel (3), thefront panel (3) defining a front side of the heater (1) and being spacedapart from the core (20) to define a front convector space (60) betweenthe front panel (3) and the core (20); and a convector structure isarranged in the front convector space (60), the convector structurecomprising a plurality of walls (61) extending between the secondoutward side (25) of the core (20) and the front panel (3) of the casing(2), the walls (61) being spaced apart to divide the front convectorspace (60) into a plurality of channels (62).
 8. A wall mountableelectric heater (1) according to claim 1, wherein the core (20) includesa sheet metal casing (21), the first protrusions (26) comprising locallyindented regions of a sheet metal panel (27) of the sheet metal casing(21); the thermal mass (30) being arranged in the sheet metal casing(21) in contact with regions of the sheet metal panel (27) proximate thefirst protrusions (26), a void (33) being formed between the thermalmass (30) and each of the first protrusions (26).
 9. A wall mountableelectric heater (1) according to claim 8, wherein the thermal mass (30)comprises a compressed mineral powder.